1. Field of the Invention
The present invention relates to a control apparatus for automobile air conditioners for controlling the humidity of the air in a vehicle compartment.
2. Description of the Prior Art
When the air in a vehicle compartment becomes dry in winter, for example, the air-conditioner is controlled to operate a humidifier to increase the humidity of the air in the vehicle compartment. In this instance, windowpanes are likely to collect moisture due to over-humidification. In order to prevent the over humidification, the present assignee has proposed a control system such as disclosed in Japanese Patent Laid-open Publication No. 56-60716 wherein operation of the humidifier is stopped when a humidity sensor detects the humidity on the inside surface of the windowpane which is larger than a predetermined value.
Such on-off control of operation of the humidifier based on the humidity or moisture content on the inside surface of the windowpane, however, does not assure a control of operation of the humidifier which is well adapted to the relative humidity of the air in the vehicle compartment. As a result, a comfortable humidity control of the air in the vehicle compartment is difficult to achieve.
In view of the foregoing difficulty, an attempt may be made to provide a humidity sensor for detecting a relative humidity of the air in the vehicle compartment so as to control the humidity in the vehicle compartment in response to output signals from the relative humidity sensor. However, such attempt will be unsatisfactory because the humidity sensor is generally not responsive to a low humidity range and hence is incapable of achieving a wide-range humidity control of the air in the vehicle compartment.